For a fourth day Australia's biggest city has been smothered with a thick, grey haze.

The smoke hangs in the sky and blocks out the sun.

You can taste it and the smell gets into your hair and your clothes.

Ash from the fires that rage around Sydney has been falling like snow flakes.

And scorched gum leaves litter many of the beaches, blown by strong winds from the frontline more than 40 miles (64 km) away.

Driving west towards the outer suburbs at the base of the Blue Mountains, the scene gets worse.

Desperation

Day almost becomes night as the smoke gets thicker.

Pollution may cause severe health problems for many Sydney residents

It is punctuated by the flashing lights of emergency vehicles, while roadblocks
stop the curious and the desperate from getting too close to the fires.

One man was arrested after breaking through one police barrier.

He said the thought of doing nothing while his house was threatened was simply too much
to bear.

This is an emergency that affects everyone in this central part of New South Wales.

Record pollution

No-one is immune from the devastation; from the hundreds of homeowners whose properties have been destroyed by the flames' relentless
advance, to those standing guard on their properties armed with only a garden
hose and bucketfuls of defiance.

I could just see this big swirling fire just coming up at us and we just ran

Sydney resident

Thousands have no power supplies while others have had to cancel their holidays or been forced to stay indoors away from the choking smog.

Pollution, meanwhile, is reaching record levels.

Dr Guy Marks from the Institute of Respiratory Medicine in Sydney says many people will be suffering.

"The main thing seems to be irritation of the eyes and nose and throat and some cough and general discomfort," he said.

"When we see pollution of this magnitude, we
would expect to see problems for patients with asthma and breathing problems."

This stricken region is battening down for another onslaught in the coming days.

A dangerous cocktail of soaring temperatures, strong winds and low levels of humidity is forecast for the weekend.

Inferno

To the south of Sydney, residents told BBC News Online how an inferno devastated
their township.

Many are angry at those suspected of causing the fires

"It's unbelievable," said one man. "We thought it was two kilometres (1.2 miles) away and all of a sudden it changed direction and came flying
this way."

"We had no warning," he added.

His neighbour believes he is lucky to be alive.

"I could just see this big swirling fire just coming up at us and we just ran," he said.

"We stopped to breathe and there was nothing there - no oxygen, nothing."

New heroes

The fire-fighters are Australia's new heroes.

Many emergency workers are volunteers, like Sandy Tibbett, who has had six hours sleep since Christmas Day.

"I was in the middle of sitting down with my daughter Kelly and the family, peeling the prawns, getting the dinner ready, then my pager went off and I dropped everything."

The fire crews' tireless efforts have provided spirited relief to people angry at arsonists suspected of causing so much of this disaster.

I had to leave in such a hurry I didn't even
have time to grab my two cats

House owner Peter Gale

So far, it is estimated that the fire-fighters have saved 11,000 homes.

Despite this, there is an army of displaced homeowners, forced out by the evacuation of settlements along the 450-mile line of fires circling Sydney.

Many are being housed at emergency centres.

Peter Gale left everything behind when the order to leave came.

"I've had word that my house is still
intact which is great news," he said.

"I had to leave in such a hurry I didn't even
have time to grab my two cats. It's pretty distressing having to leave them behind."

Bleak prospects

There is no sense of panic here; however there is clear anxiety about what will be left when the fires are finally defeated.

For example, the Royal National Park to the south of Sydney has become a blackened moonscape.

The world's second oldest national park is an Australian icon. However, at least 80% has been
eaten away by the flames and rest is almost certain to go the same way.

Sydney residents face the very real prospect that their most treasured parkland will be no more than a desolate, wide open space for years and may never fully recover.